Direct Observation of Magnetic Metastability in Individual Iron Nanoparticles

Ana Balan, Peter M. Derlet, Arantxa Fraile Rodríguez, Joachim Bansmann, Rocio Yanes, Ulrich Nowak, Armin Kleibert, and Frithjof Nolting

Phys. Rev. Lett. 112, 107201 – Published 10 March 2014

Abstract

X-ray photoemission electron microscopy combined with x-ray magnetic circular dichroism is used to study the magnetic properties of individual iron nanoparticles with sizes ranging from 20 down to 8 nm. While the magnetocrystalline anisotropy of bulk iron suggests superparamagnetic behavior in this size range, ferromagnetically blocked particles are also found at all sizes. Spontaneous transitions from the blocked state to the superparamagnetic state are observed in single particles and suggest that the enhanced magnetic energy barriers in the ferromagnetic particles are due to metastable, structurally excited states with unexpected life times.

Received 25 April 2013

DOI:https://doi.org/10.1103/PhysRevLett.112.107201

Authors & Affiliations

Ana Balan¹, Peter M. Derlet², Arantxa Fraile Rodríguez³, Joachim Bansmann⁴, Rocio Yanes⁵, Ulrich Nowak⁵, Armin Kleibert^1,*, and Frithjof Nolting¹

¹Swiss Light Source, Paul Scherrer Institut, Villigen PSI 5232, Switzerland
²Condensed Matter Theory Group, NUM, Paul Scherrer Institut, Villigen PSI 5232, Switzerland
³Departament de Física Fonamental and Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
⁴Institute of Surface Chemistry and Catalysis, University of Ulm, 89069 Ulm, Germany
⁵Department of Physics, University of Konstanz, 78457 Konstanz, Germany

^*Corresponding author. armin.kleibert@psi.ch

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Vol. 112, Iss. 10 — 14 March 2014

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